The present invention relates to a printed wiring board tester. More particularly, it relates to improvements in a probe pin adapted to be used in a printed wiring board tester and a printed wiring board which uses an improved probe pin.
As known, the printed wiring board tester examines mutual relationship in electric connection between any two points in terminal areas on individual printed wiring boards. That is, it examines whether two points in terminal areas are in a conductive state or not, and therefore functions to distinguish any improper electric connection from a proper electric connection.
In the meantime, a printed pattern formed on a printed wiring board to be examined or tested, or the disposition of groups of terminal areas varies since standardization of its lattice spacing is not sized and thus printed wiring boards are embodied with various kinds of spacing values. Furthermore, even one kind of or the same size of printed wiring boards have various lattice pitchs. Therefore, in principle, a fixture of exclusive use is required at every printed wiring board to be examined.
Conventionally, in order to avoid the abovementioned disadvantages, the tester which is provided with, for example, 0.1 inches (2.54 mm) lattice spacing as a standard is used and adaptors which are prepared for every kind of printed wiring board to be examined are selectively replaced, to be used for corresponding printed wiring boards, thereby testing various kinds of printed wiring boards.
However, since, in the above-mentioned adaptor, the probe pins are indirectly engaged with the terminal areas of the printed wiring board through adaptor pins, poor contact sometimes occurs, and in addition, the user's operation of the tester is not good, resulting in increased time and labour required for testing and preparation of testing.
First of all, the inventor has been investigating the simplification of construction from the points of view that in the case where a fixture of exclusive use examines the board without using the above-mentioned adaptor, good and high reliability of results are obtained, and very high costs are incurred for the manufacturing of individual fixtures of exclusive use since probe pins used in fixtures of exclusive use are complicated in their construction.
Although there have been various kinds of spring probes, it is common knowledge that every spring probe is fundamentally composed of four members, that is, a probe body provided with its head engaging with terminal areas, a coiled spring engaged with the probe body, a first case member telescopically holding the probe body through the coiled spring, and a second member connected at its one end with a lead and removably inserted in the first case member. Consequently, a conventional probe pin has many components and a conventional printed wiring board tester which uses these many components involves high costs in manufacturing. Further, the probe pin itself is complicated, as mentioned above, and a very small coiled spring a spring as well as functions as a portion of an electric circuit by being inserted into the first case and engaged with the lower end of the probe body. This results in many problems and a consumption in the time required for manufacturing. Since printed wiring boards have recently become miniaturized rapidly and the lattice spacings of the through-holes become the smaller due to the development of high density, it is clear that the above-mentioned disadvantages are liable to increase.
Consequently, with the above-mentioned construction of the conventional probe pin, a printed wiring board tester which fulfils pneumatic and mechanical functions of high reliability will not be expected.